Sulfate conjugation is an important pathway in the biotransformation of many neurotransmitters, hormones, drugs and other xenobiotics, and is catalyzed by cytosolic sulfotransferase enzymes designated “SULT.” SULT enzymes are encoded by a gene superfamily that, in mammals, is divided into two families: SULT1 or phenol SULTs, and SULT2 or hydroxysteroid SULTs. The SULT1 and SULT2 families share at least 45% amino acid sequence identity, while members of subfamilies within each family share at least 60% amino acid sequence identity. SULT1 subfamilies include the phenol (1A), thyroid hormone (1B), hydroxyarylamine (1C), and estrogen (1E) SULTs. SULT2 subfamilies include two hydroxysteroid SULTs, 2A1 and 2B1.
Members of the SULT1A subfamily, including SULT1A3, catalyze the sulfate conjugation of substrates such as dopamine, serotonin and other catchol monoamines, and Troglitazone. SULT1A3 is expressed in liver, brain, jejunum, kidney, and blood platelets. SULT1A3 also is referred to as “STM,” “M-PST,” or “TL-PST.”